Old chart, new chart, 4150, 4140, 4150 CMV, mil-spec, chrome lined, unlined, melonite treated, standard combat trigger, single stage after market trigger, two stage triggers, drop in triggers, Carbine, H, H2, H3 buffer, D.I. v.s. Piston, cut rifling, button rifling, hammer forged, 1:7, 1:9, 1:8, 1:8 5R, rifling groove dimension, full chrome BCG, Nickel Boron BCG, Fail Zero BCG, Eugene Stoner's original design and McNamera's effect...
Am I in the right forum? (checks address bar on browser)
For a second there I thought my browser session was hijacked and I ended up elsewhere.
mbliss57 (the OP)...
Because the AR15 enjoys an over-abundance of after-market support, there are infinite combination of standard dimension parts that can be used to build an AR15. Then it gets even more confusing because while the parts dimensions are standardized the construction details of the parts are different.
This leaves a ton of room for AR15 owners to customize and/or build their rifles to whatever way they want. Customization leads to the irrational belief that the rifle is a personal reflection of the owner. This causes arguments over gross & minute details. It's akin to how some people feel about a car, motorcycle, boat. An inanimate tool takes on more meaning than it should.
Truth be told, in the hands of a casual recreational shooter, just about any AR15 will do the job it was designed to do.
The folks who are serious competition shooters (bench, run & gun), or the real deal high-speed low-drag operators will have the practical skill and ability will be able to eke out the performance that a top-tier AR will provide.
Dragon88 gave sage advice yet again. Figure out what you want to do with your rifle, then get the rifle that fills that need. Go your firearms shop and handle a few to get a feel of them in the hand.
Once you've narrowed down your choices, let us know what make & model you are considering. Then we can help you discern the differences between them.